Fix trailing kwargs end of line comment after slash (#10297)
## Summary
Fixes the handling end of line comments that belong to `**kwargs` when
the `**kwargs` come after a slash.
The issue was that we missed to include the `**kwargs` start position
when determining the start of the next node coming after the `/`.
Fixes https://github.com/astral-sh/ruff/issues/10281
## Test Plan
Added test
